000 AXPZ20 KNHC 181603 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1512 UTC Wed Oct 18 2017 Tropical Weather Discussion for the eastern Pacific Ocean from the Equator to 32N, east of 140W. The following information is based on satellite imagery, weather observations, radar, and meteorological analysis. Based on 1200 UTC surface analysis and satellite imagery through 1430 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: Gale force winds continue over the Gulf of Tehuantepec. Recent satellite-derived wind data indicated 11 ft seas in the vicinity of the Gulf of Tehuantepec, suggesting the current gale event is still in progress. This gap wind event continues as result of a tight pressure gradient between high pressure over the eastern slopes of the Sierra Madre Mountains in Mexico. Seas remain in the range of 10 to 15 ft within the area of gale force winds. with seas of 8 ft or greater are propagating downwind from 09N to 13N between 93W and 100W. Global model guidance remains consistent in indicating that the current event has peaked and that high pressure adjacent to the eastern Gulf will weaken through Friday, allowing the pressure gradient over the Isthmus of Tehuantepec to slacken. Winds are still expected to fall below gale force just after sunrise on Thursday. However, northerly winds of 20 to 30 kt and seas of 8 to 10 ft will persist through Friday. Winds over the Gulf of Tehuantepec will pulse to strong speeds during the overnight hours on Sat night and Sun, before another gale force wind event commences Mon night. ...TROPICAL WAVES... A tropical wave is N of 06N along 85W, moving W at 10 to 15 kt. Virtually all of the convection associated with this wave remains north of the Pacific coasts of Panama and Costa Rica and inland over Nicaragua. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends W from Panama and Costa Rica to 09N84W to 08N100W to 10N114W to 10N118W. The intertropical convergence zone axis continues from 10N118W to 07N133W to beyond 08N140W. Scattered moderate and isolated strong convection is noted from 07N to 11N between 93W and 95W, from 07N to 10N between 105W and 112W and from 06N to 12N between 117W and 128W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section above for information about the ongoing Gulf of Tehuantepec gale event. A surface ridge extends SE into the waters off Baja California, producing mainly gentle to moderate NW to N winds and seas of 5 to 7 ft. The ridge will remain in place during the next few days with little change in winds and seas over the offshore waters aside from the Gulf of Tehuantepec region as described above. By Friday evening a weakening cold front and accompanying set of large NW swell will propagate into the waters W of Baja California, causing seas to build to between 8 and 12 ft across the waters N of 26N. Seas will continue to build to 14-16 ft in NW swell N of 27N Friday night. This swell event will continue propagating SE across the remaining offshore forecast waters W of Baja on Saturday. Also on Friday, expect increasing winds of 20 to 25 kt over the waters adjacent to Baja California Norte as high pressure building in the wake of the front tightens the pressure gradient over the northern forecast waters. These winds will subside on Sat. Mainly gentle to moderate NW to N winds are expected over most of the Gulf of California through early Wednesday, then winds become light and variable through Friday. Seas will stay mainly 2 ft or less, except for higher seas of 3 to 5 ft at the entrance to the gulf in SW swell. Seas will subside to 3 to 4 ft Wednesday through Thursday night, and then to 2 to 3 ft on Friday. Seas will rebuild to 3 to 5 ft near the entrance during the upcoming weekend as southerly swell reaches the area. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Moderate to fresh offshore winds will develop across the Papagayo region each night through Saturday night, accompanied by seas of 5 to 7 ft. Light and variable winds and seas of 4 to 6 ft in SW swell will prevail N of the monsoon trough, while gentle to moderate SW to W winds and seas of 5 to 7 ft in SW swell will prevail S of the trough. Long period S to SW swell will reach the area between Ecuador and the Galapagos Islands Thursday evening through Friday evening, building seas to 7 to 8 ft on Friday. REMAINDER OF THE AREA... Elsewhere, gentle to moderate winds are noted across the northern forecast waters under the influence of a ridge being weakened by an approaching cold front. Seas continue to subside across most of the region W of 110W. An area of 8 ft seas primarily in SE swell is present S of 05N W of 130W. A new set of long period S to SW swell is forecast to cross the Equator on Thursday and propagate across the far southern waters with resultant combined seas building back to 8 to 9 ft in the SW corner and far S central waters through Friday before the swell decay and seas subside below 8 ft during the upcoming weekend. Looking ahead, models agree in bringing a cold front to the far NW corner of the discussion area Wednesday evening. A significant swell event will follow the front as it weakens and dissipates. Seas will building to 10 to 17 ft over the NW waters Thursday night and Friday. The seas will spreading across all of the waters N of 08N and W of 110W by Fri evening, then across all of the waters N of the Equator and W of 108W by Sunday night. Seas of 8 ft or greater will reach all the way to 110W by early Sunday then continue to propagate SE but begin to gradually decay thereafter. $$ CAM